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EXECUTIVE SUMMARY <br />The San Luis Project is located in Costilla County, Colorado. It is an inactive precious metal <br />mining and milling operation operated by Battle Mountain Resources, Inc. (BMRI) under <br />Colorado Mine Land Reclamation Board (CMLRB) permit M -88 -112. BMRI mined and milled <br />precious metal ore at the facility from 1989 through November 1996. Since 1996, BMRI has been <br />performing surface land reclamation and closure of the facility in accordance with the CMLRB <br />permit. Current reclamation and closure are associated with completing remaining surface and <br />land reclamation of mining and milling disturbance, extracting and treating groundwater from the <br />West pit, and monitoring surface and groundwater locations within the CMLRB permit area. <br />Groundwater monitoring well M -14 is located approximately 80 feet west of the toe -of -dam at the <br />San Luis Mine Lined Tailings Facility (LTF). Historically this well has shown variability in total <br />dissolved solids (TDS) concentrations. On April 23, 2013, a groundwater sample from well M -14 <br />was collected as outlined in TR -32. Subsequent laboratory analyses showed TDS concentrations <br />which exceeded the 500 mg/l Permit Condition Value assigned to this well. On August 28, 2013, <br />a Response Plan for evaluating TDS at well M -14 was submitted to the Colorado Department of <br />Reclamation, Mining, & Safety (CDRMS) which outlined specific additional sampling activities <br />to be performed by BMRI. The Response Plan provided for additional monitoring at well M -14 <br />utilizing a low -flow sampling technique and was approved by CDRMS on September 16, 2013. <br />The first objective of the Response Plan sampling was to use a low -flow sampling technique to <br />determine if the analytical results for TDS could be stabilized. The second goal was to analyze <br />the Response Plan data and other historical records to identify if the historical variability of results <br />and concentrations of TDS in well M -14 could be attributed to any identifiable site conditions. <br />The average percent relative standard deviation ( %RSD) of all TDS samples collected during the <br />Response Plan was 1.39 percent and shows that the measured TDS concentrations have been very <br />stable throughout the Response Plan sampling. The TDS results correlated very well among field <br />measured electrical conductivity, sample duplicates, cation and anion balances, and the calculated <br />TDS. This indicates that the data collected were complete and of such quality that they could be <br />used in further analysis of potential site conditions which may be impacting the TDS <br />concentrations in well M -14. <br />TR -32 M -14 TDS Response Plan Report AES, Inc. <br />Battle Mountain Resources — San Luis, CO 1 January 2015 (Update) <br />